高功率中空微球磷酸钒锂/碳正极材料的合成及其电化学性能研究

In present project， carbon is added during the synthesis process of Li2V3(PO4)3 cathode materials in order to improve their electroic conductivity and lithium ion diffusion coefficients. The hollow structure Li3V2(PO4)3/C cathode materials are synthesized by low temperature solid-state reaction method, using V2O5 hollow microsphere prepared by soft template method. To analyze the formation mechanism of Li3V2(PO4)3/C hollow microsphere, morphologies and crystal structure of the products under different reaction stages are investigated. The effects of the synthetic conditions, hollow structure and carbon on electrochemical performance on Li3V2(PO4)3 cathode materials are studied comprehensively to find the optimum synthetic condition and carbon content, and to disclose the mechanism of action of hollow structure and carbon. The relationships among the structures, morphologies, grain sizes and electrochemical performance of cathode materails are investigated in detail to obtain hollow microsphere Li3V2(PO4)3/C cathode materials with excellent electrochemical performance. The kinetics parameters are determined using electrochemical measurement technologies. The kinetics behaviors of lithium insetion into hollow microsphere Li3V2(PO4)3 cathode materials are deeply analyzed. The structure changes of Li3V2(PO4)3 during the charge-discharge process are investigated in order to clarify the lithium ion extraction/insertion mechanisms. The significant theoretical foundation and technical support are provide to research and develop Li3V2(PO4)3 cathode materials for lithium ion batteries.

针对Li3V2(PO4)3 正极材料存在电导率低、锂离子扩散系数小的问题，本项目拟引入导电性良好的碳材料，以软模板法制备的中空微球V2O5为前躯体，采用低温固相反应法合成中空微球Li3V2(PO4)3/C 正极材料；考察不同反应阶段产物形貌和晶体结构，分析Li3V2(PO4)3/C中空微球的形成机理；综合考察合成条件、中空微球结构和碳复合对Li3V2(PO4)3正极材料电化学性能的影响，找出最优合成条件和碳含量，揭示中空结构和碳的作用机制；研究正极材料的结构、形貌、粒径、电导率等因素与其电化学性能之间的关系，获得综合性能优异的正极材料；测定电化学动力学参数，分析中空微球Li3V2（PO4）3正极材料的嵌锂过程动力学行为；研究材料在充放电过程中的结构变化，探索材料脱嵌锂机理；为锂离子电池Li3V2(PO4)3 正极材料的研究发展提供重要的理论依据和技术支持。

磷酸钒锂(Li3V2(PO4)3)具有较高的能量密度、较好的循环稳定性和热力学稳定性而成为最有前途的锂离子电池正极材料之一，但其电子电导率较低，导致倍率性能和大电流放电性能较差，限制了其在锂离子动力电池中的实际应用。.本项目针对Li3V2(PO4)3电导率低的缺陷，采用喷雾干燥法、溶胶-凝胶法等制备了磷酸钒锂/碳正极材料，通过碳包覆、多孔结构、钠离子掺杂等手段，改善了材料的倍率性能和大电流循环性能，并结合电极动力学测试分析手段，揭示了材料的脱嵌锂机理。本项目制备的中空球形Li3V2(PO4)3/C在1 C倍率下、3.0-4.3 V电压区间，首次放电容量为117 mAh/g，200次循环后，容量保持率为88.9%。Li2.6Na0.4V2(PO4)3/C在3.0-4.3 V电压范围、2 0 C倍率下，首次放电比容量高达109.7 mAh/g，1000次循环的容量衰减率为0.023%/次。在上述工作的基础上，本项目在锂离子电池锡基合金负极材料、锰酸锂正极材料、富锂锰基三元正极材料、钠离子电池电极材料等方面取得了一些进展，获得了性能优异的电极材料。.本项目发表SCI、EI、ISTP收录论文16篇，申请发明专利4项，培养研究生8名，圆满完成了研究任务，达到了预期成果考核指标要求。本项目完成的研究内容和取得的研究成果为锂/钠离子电池电极材料的研究发展提供了重要的理论依据和技术支持。